Hosta Petiole Rot

Hosta petiole rot (caused by the fungus Sclerotium rolfsii var. delphinii) appeared in the northern U.S. within the past decade. Petiole rot is very difficult to control once it appears in a production field or garden, and sclerotia of the pathogen may persist for long periods. Research in our lab by PhD candidate Zhihan Xu seeks to: 1) develop a rapid bioassay to assess cultivar resistance; 2) understand why S. rolsii var. delphinii apparently occurs primarily in the northern U.S. whereas a closely related fungus, Sclerotium rolfsii, occurs primarily in the southern U.S.; and 3) clarify genetic relatedness among phytopathogenic species of the genus Sclerotium.

A previous M.S. student in our lab, Brooke Edmunds, showed that there was a wide range of resistance to the pathogen in 18 popular hosta cultivars (2003, HortTechnology 13:302-305), documented overwinter survival of S. rolfsii var. delphinii sclerotia in Iowa (2003, Plant Health Progress doi:10.1094/PHP-2003-1201-01-RS), and found that the popular herbaceous perennial Pulmonaria is also a host of the pathogen (2003, Plant Disease 87:15). She also conducted field studies testing the effects of type and placement of organic mulch on spread of the disease.

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