Crown Rot of Pansy Caused by Myrothecium roridum. . J. M. Mullen, Department of Plant Pathology, Auburn University, AL 36849 . A. K. Hagan, Department of Plant Pathology, Auburn University, AL 36849 and L. W. Barnes, Department of Plant Pathology, Texas A&M University, College Station 77843. Plant Dis. 79:1250. Accepted for publication 19 October 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1250C.
Crown rot with total collapse of the foliage was observed on pansy (Viola ? wittrockiana Gams.) in cell packs and in landscape beds in the fall of 1994 and 1995 in Alabama. A brown, water-soaked tissue collapse progressed down the petioles of the lowest leaves into crown tissues at the soil line. In some cases the infection was localized in the crown area alone. Wounds present on some plants indicated that damage from a mechanical transplant machine may have enhanced disease incidence and/or development. Collapse of the foliage occurred suddenly once the crown was girdled. Sporodochia of Myrothecium roridum were noted on symptomatic leaf and crown tissues. Isolations from margins of decaying crowns consistently produced M. roridum on acidified PDA (aPDA). Pathogenicity tests were conducted on six wounded and six nonwounded pansies in retail six-pack trays. A pin-head size drop of spores was removed from a 2-week-old aPDA culture of the fungus with a sterile scalpel and placed onto the lower stem/crown of the plant (nonwounded) or onto the lower stem/crown of a plant where a small leaflet had been removed (wounded). Six nonwounded and six wounded pansies were kept as controls in separate six pack trays. Each of the four trays was placed separately into misted plastic bags for 4 days and watered to keep the rooting medium moist. All inoculated plants collapsed within 5 weeks postinoculation and displayed brown, water-soaked crown tissues with visible sporodochia. Myrothecium roridum was consistently isolated from margins of decaying crowns. Myrothecium roridum has not been previously reported as causing a crown rot of Viola ? wittrockiana.