Resistance of Sclerotinia homoeocarpa to Iprodione and Benomyl. A. Ronald Detweiler, Research Technician, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. J. M. Vargas, Jr., Professor, and T. K. Danneberger, Graduate Research Assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 67:627-630. Accepted for publication 15 November 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-627.

An iprodione/benzimidazole-resistant strain of Sclerotinia homoeocarpa was isolated from a creeping bentgrass putting green where dollar spot disease control with iprodione and benzimidazoles had failed. The resistant strain grew on potato-dextrose agar amended with 1,000 μg/ml of iprodione or benomyl, whereas a sensitive strain and a benzimidazole-resistant strain failed to grow on media amended with more than 1 μg/ml of iprodione. The iprodione/benzimidazole-resistant strain maintained its resistance after 4 mo away from the fungicides. Although the iprodione-resistant strain was less virulent than a sensitive and a benzimidazole-resistant strain in greenhouse trials, spray applications of iprodione and benomyl failed to control this strain under field conditions.