ABSTRACT: Isolates of Nimbya species were obtained from diseased culms of Scirpus acutus and S. validus from several locations in the Pacific Northwest and Minnesota, USA.  Ascomata with ascospores of two Macrospora species formed on autoclaved segments of Scirpus stems in axenic culture when inoculated with conidia of two Nimbya species.  Single ascospores yielded cultures of the respective Nimbya species. The taxa were demonstrated to be homothallic; isolates were pathogenic to S. acutus and S. validus.  On the basis of morphological characterization, some of the isolates from S. acutus warrant descriptions as new species:  Macrospora scirpinfestans (anamorph Nimbya scirpinfestans) and M. scirpivora (anamorph N. scirpivora).

KEYWORDS: aquatic habitat, homothallic Ascomycetes

NOMENCLATURAL NOVELTIES:
Macrospora scirpinfestans E.G. Simmons & D.A. Johnson, p. 417
Macrospora scirpivora E.G. Simmons & D.A. Johnson, p. 422
Nimbya scirpinfestans E.G. Simmons & D.A. Johnson, p. 420
Nimbya scirpivora E.G. Simmons & D.A. Johnson, p. 424