Disease Note.

A Bulb Rot of Vidalia Sweet Onion Caused by Botrytis tulipae in Georgia. D. R. Sumner, Department of Plant Pathology, University of Georgia Coastal Plain Experiment Station, Tifton 31793. R. T. Hanlin, Department of Plant Pathology, University of Georgia, Athens 30602; and J. D. Gay, Department of Plant Pathology, University of Georgia Cooperative Extension Service, Tifton 31793. Plant Dis. 78:1218. Accepted for publication 28 October 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1218A.

In 1992, Botrytis tulipae (Lib.) Lind was isolated infrequently from internal tissues of Vidalia sweet onion bulbs stored at 1 C. In 1993, oblong black sclerotia (1-2 x 2-4 mm) were observed frequently below ground under the leaf sheaths on stems of transplanted onion seedlings during the winter. B. tulipae was isolated from surface-disinfested sclerotia. Neck tissues of onion bulbs were cut and inoculated with agar blocks from cultures of B. tulipae. After 2 wk at 20 C in moist chambers, the bulbs developed neck rot and the fungus was reisolated. Gray to tan lesions in the neck were 15-40 mm x 15-30 mm, and the mycelium of the pathogen grew externally on the neck and internally between the fleshy leaves. The fungus decayed onion slices in vitro at 12-29 C. In culture, optimum growth, sporulation, and production of sclerotia occurred at 12-20 C. This is the first report of Botrytis tulipae on onion in Georgia. The fungus caused leaf spotting and tip blighting of onion in New York (2), and is a virulent pathogen on tulip bulbs (1).