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June 2018: New Dollar Spot Pathogens, USGA Central Region Update

Posted on June 12th, 2018

Dollar spot can cause considerable damage to playing surfaces if not properly managed.

Rutgers University and the USDA recently completed work to reclassify the ubiquitous dollar spot pathogen, previously classified as Sclerotinia homoeocarpa. Phylogenetic testing using three nucleotide sequence markers from the fungus indicated that S. homoeocarpa is not actually a species of Sclerotinia or any other established fungal genus.

As such, a new fungal genus called Clarireedia was established. The new name is in honor of Dr. Reed Funk, the famous turfgrass breeder from Rutgers University. Within this genus are the following four unique species:

C. bennettii – Named after Dr. F.T. Bennett, the mycologist from the United Kingdom that identified the fungus in 1937

C. homoeocarpa – A homage to the original species classification

C. jacksonii – Named after renowned turfgrass pathologist Dr. Noel Jackson from the University of Rhode Island

C. monteithiana – Named after Dr. John Monteith, USDA turf pathologist and former USGA Green Section Director

Initial reports indicate that these unique pathogen species vary in distribution and in the turfgrass hosts they infect. C. bennettii and C. homoeocarpa occur primarily on red fescue in the United Kingdom, whereas C. jacksonii and C. monteithiana appear to be more widespread and can infect both cool- and warm-season turfgrass. Additional Clarireedia species characteristics will certainly be investigated in the coming years now that turfgrass pathologists have an accurate way to distinguish among the fungal isolates. Understanding the differences among the causal organisms will reveal helpful information to further fine-tune dollar spot management programs.

In the meantime, turfgrass managers should continue to rely upon currently accepted best management practices for minimizing dollar spot damage. The USGA article “Getting the Upper Hand on Dollar-Spot Disease” provides effective control measures to mitigate dollar spot injury. For those wanting to delve deeper into the dollar spot taxonomic paper, it can be downloaded for free here.

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