Dothistroma needle blight in protected pine forests in Italy

Widespread and locally severe foliar symptoms resembling Dothistroma Needle Blight (DNB), one of the most important infectious diseases of forest trees worldwide, were recently observed in La Sila Massif, a mountain plateau covered with native forests of Pinus nigra subsp. laricio in La Sila National Park, Southern Italy. At the same time, DNB symptoms were observed in Pinus cembra and Pinus mugo forests in the Paneveggio-Pale di San Martino Nature Park and in Val Sarentino, Northeastern Italy. Defoliation was extensive at all sites and severe on the majority of plants of affected species, both adult trees and renovation. In particular on Pinus cembra, the disease was so serious as to locally threaten the species' reproduction and survival, an unusually heavy damage on this host. Species-specific real time PCR diagnostics, recommended by EPPO, was applied to needle samples from these sites and the presence of Dothistroma septosporum was ascertained, while Dothistroma pini, the morphologically identical congeneric species causing the same disease, was not detected. The pathogen was isolated from conidiomata and species attribution was confirmed by sequencing of the ITS region. In addition, a culture independent survey based on the same molecular assays was carried out in other areas of Northern, Central and Southern Italy, where pines of various species were affected by similar symptoms, and gave negative results for both Dothistroma species. Results show that D. septosporum currently has in Italy a much larger distribution and host range than reported and is associated to life-threatening damage to native pine species growing in established populations for in situ conservation of genetic resources, which would require an update of specific conservation actions.