Six ophiostomatoid fungi, i.e., Ceratocystiopsis minuta, Ceratocystis laricicola, Ophiostoma brunneo-ciliatum, O. laricis, O. piceae and Ophiostoma sp., were isolated from the galleries of Ips cembrae on Japanese larch (Larix kaempferi) logs in central Honshu, Japan. Japanese larch trees approximately 30 yr old were inoculated with all six fungi. Ceratocystis laricicola produced the largest lesions on the inner bark around the inoculation point and the largest dry zone in the sapwood. Furthermore, C. laricicola was the only fungus associated with I. cembrae that had the ability to kill Japanese larch, death occurring in 30-yr-old trees within 3.5 mo after inoculation.

We isolated ophiostomatoid fungi from bark beetles infesting Pinus densiflora and their galleries at 24 sites in Japan. Twenty-one ophiostomatoid fungi, including species of Ophiostoma, Grosmannia, Ceratocystiopsis, Leptographium, and Pesotum, were identified. Among these, 11 species were either newly recorded in Japan or were previously undescribed species. Some of these fungal species were isolated from several bark beetles, but other species were isolated from only a particular beetle species. Thus, it is suggested that some ophiostomatoid fungi have specific relationships with particular beetle species. In addition, fungus–beetle biplots from redundancy analysis (RDA) summarizing the effects of beetle ecological characteristics suggested that the association patterns between bark beetles and the associated fungi seemed to be related to the niches occupied by the beetles.

We made inoculations to determine the comparative virulence of blue-stain fungi isolated from Japanese red pine (Pinus densiflora Sieb. & Zucc.). Based on the symptoms caused by each fungus, the most virulent fungus was Leptographium wingfieldii. Also, Ophiostoma minus was relatively virulent while lesions induced by some species did not differ from those in the control treatment. Based on the results, we concluded that the pathogenicity of the blue-stain fungi varied widely, and thus their impact on the host most likely varies too.