Multiple functions have been attributed to forests covering 30% of the land area. Since diverse and sustainable forests are required for benefits from ecological services, degradation of forests due to pests and diseases is one of the most important problems that need to be solved. Since fungi occupy more than 3/4 of the pathogenic microorganisms of plant diseases, pathogenic fungal control is necessary for the healthy and sustainable forest management. In recent years, instead of conventional chemical control, there has been a shift towards integrated pest management methods to reduce the effects of environmental pollution and ecosystem disturbance. Unlike agricultural crops, trees, which are the main components of forests, are perennial and have large individual sizes, and are complex and difficult to manage due to their natural conditions. In order to establish a management method based on ecological control and low environmental load, it is necessary to understand ecological characteristics of pathogens. In this article, I would like to introduce studies on taxonomy and phylogeny, anatomical pathogeny, and molecular ecology conducted for the comprehensive understanding of ecological characteristics of tree pathogens.

Multiclavula vernalis, a lichenized clavarioid fungus, was newly recorded in Japan with descriptions and illustrations of the fruiting bodies and the thalli based on specimens collected in Nagano Prefecture. This report also contains the sequence of nrDNA ITS region, the results of the molecular phylogenetic analyses, and the information on the multispore culture. Fruiting bodies of M. vernalis were scattered on the ground of Andosols in the subalpine zone in Japan, and the lichenized thallus was undifferentiated or globular and composed of spherical algal cells surrounded by fungal hyphae. The photobiont seemed to be a green alga and contained many vesicles, possibly lipids.

A rare cup fungus, Microstoma apiculosporum was reported from Japan for the first time. This species is characterized by the ascospores with bipolar hemispherical apiculi, which is a unique feature in the genus Microstoma. This species was originally described from central Taiwan in 2004 and has not been reported from outside of the type locality. We provided its morphological description based on the vital taxonomic method and chemical reaction. Furthermore, we found a cell layer of textura angularis–globulosa between the medullary excipulum and hymenium near the margin, and the cyanophobic perispores that formed the bipolar apiculi of the ascospores.

A powdery mildew that occurred on leaves of Cerasus kumanoensis (Kumanozakura) was collected and identified as Podosphaera prunigena by molecular phylogenetic analysis and morphological comparison. Based on the observation of type specimen, the description of P. prunigena was emended. Morphological features of conidia and conidiophores not reported in the original description of P. prunigena are described. This is the first report of powdery mildew on C. kumanoensis.