Virulence of Dothistroma septosporum and D. pini on Pinus nigra and P. mugo under conditions of natural infection

Dothistroma needle blight (DNB) is a severe needle disease of pines worldwide, caused by two closely related species, Dothistroma septosporum and D. pini. The two fungal species are similar not only in their morphological characteristics, but also cause very similar symptoms in their hosts, and have a similar ecology. The aim of this study was to compare the virulence of the two Dothistroma species in natural infection experiments on 2-year-old seedlings of two DNB susceptible pine species, Pinus nigra and P. mugo, in two seedling stands for each pathogen species. The virulence of the pathogens and presence of symptoms (symptomatic needles, red bands and acervuli) were assessed after 2 years of exposure to inoculum. The incidence of seedlings with DNB symptoms was 65