China, Hainan Province: East Harbour National Nature Reserve, on diseased leaves of Schimasuperba, 23 May 2021, Z.X. Zhang (holotype HSAUP212201; ex-type living culture SAUCC212201).

Name refers to the genus of the host plant Schimasuperba.

Leaf spots irregular, pale brown in centre, brown to tan at margin. Sexual morph not observed. Asexual morph on PDA: Conidiomata solitary, scattered, black, raising above surface of culture medium, subglobose, exuding black conidial droplets from central ostioles after 10 days in light at 25 °C. Conidiophores cylindrical, hyaline, smooth-walled. Conidiogenous cells 9.0–16.5 × 1.2–2.2 μm, phialidic, ampulliform, discrete, hyaline, smooth, thin-walled. Conidia 18–24 × 4.5–6.0 μm, mean ± SD = 20.5 ± 1.1 × 5.5 ± 0.4 μm, fusiform, tapering at both ends, 4-septate; apical cell 2.0–4.0 μm long, conical, hyaline and smooth-walled; three median cells doliiform, 12.5–15.5 μm long, mean ± SD = 14.2 ± 0.7 μm, olivaceous, rough-walled, upper second cell 3.8–5.3 μm long, upper third cell 3.4–5.0 μm long, upper fourth cell 4.4–5.4 μm long; basal cell 2.2–4.5 μm long, conical, hyaline and smooth-walled; apical appendage 7.0–12.5 μm long (mean = 9.2 μm), single, unbranched, central, tubular, filiform; basal appendage 2.5–5.0 μm long, single, unbranched tubular, filiform.

Colonies on PDA 39.0–45.0 mm in diameter after 15 days at 25 °C in darkness, growth rate 2.5–3.0 mm/day, irregularly circular, raised, dense surface with lobate edge, zonate in different sectors, light brown at the margin, brown at the centre; reverse brown at the margin, dark brown at the centre.

China, Hainan Province: East Harbour National Nature Reserve, 23 May 2021, Z.X. Zhang. On diseased leaves of Schimasuperba, paratype HSAUP212202, living culture SAUCC212202; on diseased leaves of Schimasuperba, paratype HSAUP212203, living culture SAUCC212203.

Monochaetiaschimae is introduced based on the multi-locus phylogenetic analysis, with three isolates clustering separately in a well-supported clade (BI/ML = 0.99/96). Monochaetiaschimae is phylogenetically close to M.castaneae from leaves of Castaneamollissima, M.ilicis from leaves of Ilex sp., and M.junipericola from twigs of Juniperuscommunis. However, Monochaetiaschimae differs from M.castaneae by 148 nucleotides (11/463 in ITS, 89/743 in tub2 and 48/403 in tef1), from M.ilicis by 94 nucleotides (18/526 in ITS, 32/698 in tub2 and 44/456 in tef1), and from M.junipericola by 91 nucleotides (10/524 in ITS, 40/411 in tub2 and 41/304 in tef1). Furthermore, they are distinguished by hosts and conidial sizes (18.0–24.0 × 4.5–6.0 μm in M.schimae vs. 18.8–27.3 × 4.7–6.6 μm in M.castaneae vs. 20.0–27.0 × 5.0–8.0 μm in M.ilicis vs. 22.0–28.0 × 5.0–7.0 μm in M.junipericola). In morphology, Monochaetiacastaneae differs from M.schimae by the colour of colonies (cinnamon vs. brown), Monochaetiailicis differs from M.schimae by the colour of median cells (brown vs. olivaceous), and M.junipericola differs from M.schimae by longer conidiogenous cells (10.0–30.0 μm vs. 9.0–16.5 μm) (de Silva et al. 2017; Crous et al. 2018; Jiang et al. 2021b).