The main differences between Neonectria s. str. and Corinectria is the perithecial wall anatomy as described by Chaverri et al. (2011). Neonectria s. str. fits Booth’s classification of perithecial anatomy of the Nectriagalligena/coccinea-group, while Corinectria resembles that of the phylogenetically distantly related Nectria mammoidea-group (Booth 1959). The perithecia in Neonectria s. str. are subglobose to broadly obpyriformwith blunt apex and sometimes papillate ostiolar area,generally smooth and shiny, 35–50 μm. The perithecial wall is composed of 2–3 regions or layers; the outer consisting of thick-walled, round cells in section and face view (Booth 1959; Chaverri et al. 2011; Hirooka et al.2013). In contrast, perithecia in Corinectria are globose to subglobose, with a smooth and shiny surface and with papilla or a darker area in the ostiolar region. Corinectria also has perithecial walls that consist of 2–3 regions. Cells of the outer-wall region are oblong cylindrical and form a palisade perpendicularly oriented to the locule (Fig. 4d–f). Species of both genera produce abundant fusiform and hyaline microconidia but only Neonectria species produce chlamydospores. Corinectria spp. are known as strong to weak pathogens of only a few genera of conifers, while Neonectria species occur mostly on broadleaf hosts, sometimes conifers, as pathogens or saprophytes.