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Pathogen Biology

Currently, the dollar spot pathogen is classified as Sclerotinia homoeocarpa. However, this classification is under revision, and once completed, the fungus may be reclassified as Lanzia, Moellerodiscus, or Rutstroemia. Reasons for the proposed reclassification of the fungus are as follows: 1) failure of S. homoeocarpa to form sclerotia which is a characteristic of Sclerotinia spp., 2) apothecial morphology of S. homoeocarpa differs from that of other Sclerotinia spp., 3) electrophoretic protein patterns and ribosomal DNA of S. homoeocarpa are similar to those of Lanzia, Moellerodiscus, and Rutstroemia.

In culture, S. homoeocarpa produces mycelium that is compact, and white. In comprehensive studies of the fungus conducted in the 1930s, isolates of S. homoeocarpa from the U.S. and Australia were sterile, while several isolates from Great Britain produced ascospores, conidia, and microconidia. S. homoeocarpa is the only member of the Sclerotinia genus that does not produce a sclerotium. Instead, the fungus produces a matrix of vegetative hyphae referred to as a stroma that can survive for long periods in grass clippings, thatch or soil.