Sixteen species and two varieties of lichenicolous fungi are reported from Rhizoplaca s. lat. Four species and one variety are described as new to science: Caeruleoconidia ahtii Zhurb. (on Rhizoplaca s. str.), with hyaline to pale greyish turquoise, comparatively large conidia; Cercidospora mongolica Zhurb. & Cl. Roux (on Rhizoplaca s. str.), with a reddish brown (above) to pale brownish grey to colourless (below) exciple, mostly 4-spored asci, and (0‒)1(‒2)-septate ascospores, mostly 23‒28.5 μm long; C. tyanshanica Zhurb. & Cl. Roux (on Protoparmeliopsis and Rhizoplaca s. str.), with a uniformly grey exciple, mostly 4-spored asci, and (0‒)1(‒2)-septate ascospores, mostly 25.5‒31.5 μm long; Stigmidium pseudosquamariae Zhurb. (on Protoparmeliopsis), inducing brown cerebriform galls, with consistently immersed ascomata and well-developed pseudoparaphyses of type b sensu Roux & Triebel (1994); and Arthonia clemens var. peltatae Zhurb. (on Protoparmeliopsis), with a brown epihymenium without grey shade. An unidentified species of Leptosphaeria growing on Protoparmeliopsis peltata, and Lichenostigma cf. chlaroterae growing on P. peltata and Rhizoplaca chrysoleuca are briefly characterized. Arthonia clemens is newly reported for Kazakhstan, Kyrgyzstan and the Republic of Sakha (Yakutia) in Russia; Cercidospora melanophthalmae is new to Kazakhstan, Kyrgyzstan and Mongolia; Didymocyrtis rhizoplacae is new to Russia; Lichenoconium lecanorae and Muellerella erratica are new to Kyrgyzstan; Stigmidium squamariae s. lat. is new to Kazakhstan, Kyrgyzstan and Turkmenistan. Didymocyrtis rhizoplacae is documented for the first time on Rhizoplaca subdiscrepans, and Pyrenidium actinellum s. lat. on Protoparmeliopsis. A key to 36 species of lichenicolous fungi and lichens known to occur on Rhizoplaca s. lat. is provided.

Two species of lichenicolous fungi are described as new to science: Lichenotubeufia etayoi Zhurb. (on Trachyderma), with light orange perithecia up to 360 μm diam., non-fasciculate excipular hairs, and 10–13-septate ascospores, 110–162 × 3–5 μm; and L. tibellii Zhurb. (on Coccocarpia), with light orange perithecia up to 275 μm diam., non-fasciculate excipular hairs, and 5–12-septate ascospores, 50–100 × 3–4.5 μm. An updated key to the species of Lichenotubeufia is provided.

Three species of lichenicolous Opegrapha s. lat. are newly described, all apparently host-specific at genus level. Opegrapha arthoniicola Coppins & S. Y. Kondr. is described from western Britain and Ireland, where it grows on the thallus of Arthonia radiata on Corylus bark; it has small clustered ascomata, asci that are usually 6-spored and rather small ascospores (10.5–)12.5–14.5 μm in length. Opegrapha sawyeriana Coppins occurs on the thallus of Coniocarpon cinnabarinum, also on Corylus bark, from oceanic western parts of Scotland, Ireland and southern England; in comparison to O. arthoniicola it has smaller, often scattered ascomata with a pigmented basal layer, 8-spored asci and slightly larger ascospores 13–14.5(–16) μm in length. Opegrapha hochstetteri Coppins has been found on thalli of Verrucaria hochstetteri and V. muralis on calcareous rocks and stonework in southern England and Luxembourg; collections were formerly identified as Opegrapha rupestris Pers. but it differs from this species by narrower ascomata with a persistent narrow slit, normally 6- rather than 8-spored asci and ascospores with pigmentation in the spore wall rather than the perispore. Lifted from synonymy is Opegrapha opaca Nyl., which inhabits the thallus of Verrucaria nigrescens and V. viridula on calcareous rocks and stonework, and is so far recorded from southern England, Luxembourg, France, northern Spain and Israel. The hosts of the European species of lichenicolous Opegrapha on Verrucaria s. lat. on calcareous rocks (O. hochstetteri, O. opaca and O. rupestris) belong to different phylogenetic lineages within the Verrucariaceae. A key is also provided to the lichenicolous species of Opegraphaceae currently known from Great Britain and Ireland.