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% and 76% for P. nigra and P. mugo, respectively. No difference was found between D. septosporum and D. pini in any of the three DNB symptoms evaluated on seedlings of P. mugo. However, symptoms of disease differed between the two Dothistroma species on P. nigra. Variables that reflect the intensity of disease development, the number of red bands and acervuli per needle, showed a difference in virulence between D. septosporum and D. pini, but only in the case of the host species P. nigra. The results suggest that the virulence of the two Dothistroma species could be affected by host pine species and that there are differences in the susceptibility of individual pine species to D. septosporum and D. pini. Further factors could affect the virulence of these pathogens, including isolate origin, climatic or environmental factors.

针叶枯病 (DNB) 是世界范围内松树的一种严重针叶病，由两个密切相关的物种引起，即Dothistroma septosporum和D. pini。这两种真菌不仅形态特征相似，而且在宿主中引起的症状也非常相似，并且具有相似的生态。本研究的目的是在两种 DNB 易感松树（黑松和黑松）的 2 年生幼苗的自然感染实验中比较两种Dothistroma物种的毒力，在每个病原体物种的两个幼苗林中。接触接种物两年后，评估病原体的毒力和症状（症状针、红带和鹿角虫）的存在。P. nigra和P. mugo幼苗出现 DNB 症状的发生率分别为 65% 和 76%。在对P. mugo幼苗进行评估的三种 DNB 症状中，没有发现D. septosporum和D. pini之间存在差异。然而，黑杨上的两种Dothistroma物种之间的疾病症状有所不同。反映疾病发展强度的变量、每根针的红带和鹿角数量显示了D. septosporum和D. pini之间的毒力差异，但仅限于宿主物种P. nigra的情况。结果表明，两种松线虫的毒力可能受到寄主松树种的影响，并且不同松树品种对隔孢线虫和松线虫的敏感性存在差异。其他因素可能会影响这些病原体的毒力，包括分离源、气候或环境因素。