Hyphae hyaline, septate, smooth-walled, 1.0–2.5 µm wide. Phialides hyaline, single, arising from undifferentiated hyphae and often curled toward the hyphae on which they are borne, occasionally on basitonously or penicillately branched conidiophores, cylindrical to ampulliform, constricted below the collarette, 9.0–22 × 2.0–3.5 μm (mean ± SD: 15 ± 4.0 × 2.5 ± 0.5 μm). Collarettes indistinct, cup-shaped, 2.0–3.5 μm deep. Conidia hyaline, clavate to ellipsoidal, with a truncate base, 3.5–4.5 × 2.5–3.5 μm (mean ± SD: 4.0 ± 0.5 × 3.0 ± 0.5 μm) on MLA, 3.5–4.5 × 2.0–3.0 μm (mean ± SD: 4.0 ± 0.5 × 2.5 ± 0.5 μm) in slide culture on MLA, slimy and accumulating in small groups at the apices of the phialides. Chlamydospores, ascomatal initials, and ascomata not observed.

Neobulgaria koningiana is based on Phialophora alba, but the epithet “alba” is unavailable for this species because of the validly published Neobulgaria alba, the name applied by Johnston et al. (2010) to an apothecial species from kiwifruit vines. Although the kiwifruit pathogen was identified originally as Ph. alba, the ex-type culture of this species (CBS 112.43) was identified as belonging to Paecilomyces based on the comparison of ITS sequences (Johnston et al. 2010). The isolate characterized in our study (MUCL 9775) is derived from CBS 112.43 and conforms closely to the descriptions of the Ph. alba provided by van Beyma Thoe Kingma (1943) and Schol-Schwarz (Citation1970). It differs from N. alba in producing smaller, more spherical conidia (3.5–4.5 × 2.5–3.5 μm vs. 4.5–5 × 3–3.5 μm) and phialides that are solitary or grouped on conidiophores with fewer levels of branching. It seems probable, therefore, that the strain representing CBS 112.43 sequenced by Johnston et al. (2010) was a contaminant.

THE NETHERLANDS. Amersfoort, wood of Fagus sylvatica, H.C. Koning (holotype CBS H-7564; isotypes CBS H-7565, CBS H-7566, CBS H-7567). Ex-type culture CBS 112.43 = IHEM 5885 = MUCL 9775.