Krombholziella rugosa is a species described for the North of France, only found between 1970 and 1975. This may be a rare species, but the lack of observations may also be due to confusions with other similar or potentially synonymous species. Taxonomic review and search efforts to determine current population size and distribution are needed so the species is assessed as Data Deficient (DD).

Only species in the genus Krombholziella, K. rugosa was assigned to this genus in a taxonomic review in 1985. All other species that previously belonged to this genus have since been transferred to other genera (Leccinellum and Leccinum). Synonyms: Leccinum rugosum and Boletus rugosus Fr. (1835) (nom. illegit., not to be confused with Boletus rugosus Jacq. (1774), synonym of Ganoderma lucidum). (Species Fungorum, 2023)

Only known from the north of France (Roost-Warendin and Carvin, Auchel and Lapugnoy in Pas-de-Calais).

Only known from 4 locations in the North of France, collected between 1970 and 1975 (Bon and Van Haluwyn,1981, GBIF.org 2023). The species has not been found since, and no more information is available. It may be rare, but since it is conspicuous and found in a region with generally high searching efforts, it is also possible that it may be confused or synonymous with another species (e.g. Leccinum sp.) and forgotten to science. Therefore it is not possible to estimate current population size.

Terrestrial species, found in the presence of Betula, Salix and Calamagrostis epigejos (Bon and Van Haluwyn,1981).

Unknown.

Taxonomic review is needed to confirm the validity of this species and its placement in the Krombholziella genus. Targeted search efforts on known locations and other areas of suitable habitat are needed to establish distribution and current population size.